1. Field of Invention
This invention relates to a heat-insulating member interposed between a bus bar substrate including an electrical power circuit and a control circuit substrate including a control circuit for controlling the circuit components connected to the electrical power circuit, and also relates to a circuit assembly utilizing the heat-insulating member to be installed in, for example, a distribution unit for distributing an electrical power from a common electrical power source on a vehicle among a plurality of electronic units.
2. Description of Related Art
Recently, a number of electronic units are installed on a vehicle such as a motor vehicle and a distribution unit is generally used for distributing an electrical power from a common electrical source on a vehicle among the respective electronic units. A circuit assembly to be installed in the distribution unit has been known. Such circuit assembly, as disclosed in, for example, Japanese Patent Public Disclosure 2002-330526, includes a stacked circuit section (bus bar substrate) in which bus bars constituting an internal circuit are stacked through insulation plates at plural layers. The bus bar on a lower layer of the stacked circuit section is bent to form a tab terminal. The tab terminal is inserted into a receiving-aperture in the stacked circuit section and projects from a front side of the aperture. A tab terminal of a relay is connected to the tab terminal of the bus bar through a junction terminal having a female type-coupling portion on the opposite ends, so that the relay is detachably connected to the internal circuit.
An occupation area for arranging the distribution unit on a vehicle body tends to be decreased every year. On the other hand, a number of circuit components have been mounted on the bus bar substrate and control circuit substrate. In association with this tendency, it has been eagerly required to efficiently arrange the circuit components and to downsize the contribution unit and the circuit assembly to be installed in the contribution unit.
However, in the distribution unit and circuit assembly disclosed in the above Patent Document 1, if the circuit components to be mounted on the respective substrates increase in number, the circuit components are disposed on the respective substrates individually and useless spaces will increase. This will make it difficult to efficiently arrange the circuit components and to maintain a compact structure of the circuit assembly.
Thus, if the control circuit substrate is disposed in parallel to the bus bar substrate and the circuit components to be mounted on the respective substrates are efficiently arranged in the space defined between both the substrates, it will be possible to maintain compact structures of the distribution unit and circuit assembly.
However, in such a double-deck structure in which the bus bar substrate and control circuit substrate are disposed in parallel to each other and the circuit components are arranged between both the substrates, heat generated from the circuit component such as a relay that is mounted on the bus bar substrate and has a relatively high heating value affects the control circuit substrate. In addition, this double-deck structure makes electrical connection between both the substrates when pin-like terminals standing from the bus bar substrate are forcedly inserted into through-holes in the control circuit substrate. This will make it difficult to insert the pin-like terminals projecting upward from the upper surface of the bus bar substrate into the through-holes in the control circuit substrate correctly and positively. Consequently, the pin-like terminal will tend to be buckled, bent, or deformed upon insertion. This will lose reliability in electrical connection.
In view of the above problems, an object of the exemplary invention is to provide a circuit assembly in a compact structure and a heat-insulating member that can be easily installed in the circuit assembly and constructed effectively in a thermal design.